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A novel luminescent Cu(II)–organic framework, {[Cu(asba)(3bpmo)0.5(H2O)]·H2O}n (1), was obtained through the assembly between copper(II) and 2-amino-5-sulfobenzoic acid (H2asba) in the presence of an auxiliary flexible ligand, N,N′-bis(3-pyridylmethyl)oxalamide (3bpmo). 1 is a 2D (6, 3) topological network, which further extends into a 3D supramolecular network via hydrogen and chalcogen bonds. An indirect bandgap exists in 1. 1 shows high framework stability in common solvents and reversible dehydration–rehydration behaviour. Remarkably, 1 is an especially rare example that exhibits novel solvent-dependent luminescence sensing properties. In DMF, 1 shows selective and sensitive fluorescence “turn-off” sensing of Fe3+ over a number of coexistent metal cations. 1 could also be used as a potential selective and sensitive probe for HCO3− among a variety of interfering anions. Furthermore, 1 shows discriminative sensing of HCO3− over CO32−. In water, 1 shows a quite different fluorescence sensing behaviour from that in DMF. 1 cannot sense Fe3+ and HCO3− in aqueous medium. It is fascinating that 1 shows selective and efficient fluorescence “turn-on” sensing of Al3+ accompanied by a bathochromic shift of the emission peak in water. The limit of detection (LOD) for Al3+ reaches the 0.80 μM (0.02 ppm) level.

An indene-chalcone-based fluorescence probe 1 was synthesized and characterized. Under physiological conditions (containing 5% DMSO), probe 1 showed satisfactory stability with a low background signal and recognized carboxylesterases (CEs) based on the catalytic hydrolysis of ester groups, releasing a significant green fluorescence. Probe 1 presents several features including a short response time (within 20 min), low detection limit (1.3 × 10

Novel high-performance non-labeled fluoro-sensing micro/nano-optics require lithographically fabricable stimuli-fluorescence transductive materials well-tailored in molecular levels, towards superior processibility, stability, sensitivity, on-chip integration and portability, and real-time and in situ analysis. Here, aggregation-induced-emission fluorophores with oxetane groups (AIEoxes) and their covalently co-crosslinkable epoxy composites are customized for the fabrication of micro/nano-devices via single/multi-photon lithography. The oxetane modification increases the AIEoxe miscibility in the epoxy matrix (doping ratio up to 10 wt%), and consequently improves the as-formed devices’ quality, stability, and fluorescence intensity and sensitivity. The multi-color-AIEoxe polymeric micro/nano-devices allow fluorescence-resonance-energy-transfer among AIEoxes, which enables sensitive and specifically spectral detection of VOCs. With the micro/nano-waveguide configuration, solvent-responsive AIE fluorescence and evanescent-field/refractive-index sensing enhance the AIE-fluorescent detection of trace organic solvents in aqueous solutions (detection limit, ∼0.004% v/v, tetrahydrofuran/water) and their facile integration in functional micro/nano-systems like optofluidics.

A novel naphthalene based fluorescence probe NBDH was designed and synthesized. Probe NBDH exhibited highly selective and sensitive responses towards Al3+ in HEPES-NaOH buffer solution (pH = 7.4). In addition, the detection of NBDH to Al3+ could be achieved through dual channels embodied in significant fluorescent turn-on signal and ratiometric absorbance response. The stoichiometry ratio of NBDH-Al3+ was 1:1 by fluorescence job’ plot and binging mechanism was further varified by the FT-IR, NMR titration and HRMS. Furthermore, NBDH was achieved in real sample detection, and a series of color test paper were developed for visual detecting Al3+ ions.

A simple naphthalene derivative, 6-hydroxy-2-naphthohydrazide (NAH), was designed and synthesized through two facile steps reactions with the 6-hydroxy-2-naphthoic acid (NCA) as the starting material. In neat H2O (10% 0.01 M HEPES buffer, v/v, pH = 7.4), probe NAH showed a highly selective and sensitive response towards Fe3+ via perceptible color change and displayed “turn-on” dual-emission fluorescence response for Cu2+. The binding stoichiometry ratio of NAH/Cu2+ and NAH/Fe3+ were all confirmed as 1:1 by the method of fluorescence job's plot and UV–Vis job's plot, respectively. Probe NAH can be used over a wide pH range for the determination of Fe3+ (2.0–10.0) and Cu2+ (6.0–10.0) without interference from other co-existing metal ions. A possible detection mechanism was the hydrolysis of NAH upon the addition of Fe3+ or Cu2+, thereby leading to the formation of 6-hydroxy-naphthalene-2-carboxylic acid (NCA) which was further confirmed by the various spectroscopic techniques including FT-IR, 1H NMR titration and HRMS. Moreover, NAH was successfully applied to the detection of Cu2+ and Fe3+ in tap water, ultrapure water and BSA.

A novel quinoline-based Schiff base fluorescent sensor BQPA had been synthesized and characterized by common spectroscopic methods. It showed highly sensitive fluorescent enhancement (300-fold) and ratiometric absorbance for the determination of Al3+ with low detection limits of 31 nM in CH3CH2OH/H2O (1: 9, v/v) solution. The stoichiometry of the BQPA–Al3+ complex was 1:1, determined by Job plots curve and further confirmed by HRMS, 1H NMR titration and FT-IR spectrum. Moreover, the potential application of BQPA in the detection of Al3+ was estimated in real water samples.

A new naphthalene-quinoline based chemosensor L was prepared and structurally characterized. L exhibited excellent selectivity and sensitivity to Al3+ through distinct fluorescence enhancement (335-fold) and ratiometric detection in DMF/H2O (v/v, 1/9) based on the combined mechanisms of ESIPT and CHEF. The recognizing behavior of L toward Al3+ had been investigated in detail through Job's Plot, FT-IR, HNMR, and HRMS analysis. The limit of detection (LOD) for Al3+ was as low as and 3.67 × 10−8 M. L was successfully applied in real sample detection and construction of molecular logic gate. Moreover, L was verified to be of low cytotoxicity and good imaging characteristics for the detection of Al3+ in cells HSC.

In this study, we developed a fluorescence-enhanced probe (1) based on a simple Schiff-based condensation reaction for Cu2+ selection. We investigated its distinct recognition mechanism through mass spectra, 1H NMR studies, and DFT calculations. The imaging and costaining experiments indicated that the probe could successfully image lysosomal Cu2+.

Amino-MIL-53(Al) (NH2-MIL-53(Al)) nanocrystals were successfully obtained through microwave ultrasound-assisted method. The structure and morphology of the as-synthesized NH2-MIL-53(Al) nanocrystals were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption isotherms, respectively. Upon excitation at 388 nm, the as-synthesized NH2-MIL-53(Al) nanocrystals show strong emission peak at 454 nm in n-octane solution at room temperature. Meanwhile, the fluorescence explorations revealed that NH2-MIL-53(Al) can selectively detect organosulfur compounds, including thiophene and benzothiophene through quenching effect in model fuel, with high quenching constant and low detection limit. This work presents a facile platform for the detection of organosulfur compounds in model fuel.

A novel naphthalimide-based colorimetric and fluorescent turn-on chemosensor for Al3+ was synthesized and characterized with spectroscopic techniques. In MeOH solution, BPAM showed high selectivity and sensitivity to Al3+ by a 60-fold fluorescence enhancement and blue-shift absorption with visible color changes attributed to the contribution of chelation enhanced fluorescence (CHEF) and inhibition of intramolecular charge transfer (ICT). A 1:1 BPAM-Al3+ complex confirmed by job's plot and HRMS with a binding constant of 6.37 × 104 M- 1, and the detection limit for Al3+ was as low as 1.59 × 10- 7 M. BPAM was successfully applied in real sample detection and assessing the existence of Al3+ by a colorimetric method on filter paper. Furthermore, the fluorescent signals of BPAM were designed to construct an INHIBIT molecular logic gate.

One zinc-based coordination polymer was synthesized by a solvothermal method using zinc nitrate and 1,4-bis(1-imidazolyl)benzene (bib) ligand, {Zn(bib)·(SO4)·(H2O)}n (1). The fluorescence test results showed that compound 1 had a good fluorescence quenching effect on antibiotics and metal ions, especially norfloxacin and Fe3+. The limit of detection is calculated to be 7.04 ​μmol/L for norfloxacin. The results of the anti-interference experiment show that it selectively detect norfloxacin. Meanwhile, compound 1 has a good adsorption effect on methyl orange due to the electrostatic interactions and the different molecular sizes.

A new schiff-base receptor L based on naphthalimide had been investigated as a selective and sensitive chemosensor for Al3+ in CH3OH. Upon addition of Al3+, L showed a 39-fold enhancement at 508 nm with colorimetric and fluorometric dual-signaling response which might be induced by the integration of ICT and CHEF. A 1:1 stoichiometry for the L-Al3+ complex was formed with an association constant of 1.62×104 M−1, and the limit of detection for Al3+ was determined as 7.4 nM. In addition, the potential utility of L in sensing Al3+ was also examined in real water samples.

Sensing and detecting toxic pollutants like Fe3+, chromate anions and trinitrophenol (TNP) in water are especially important due to their hazardous effects on environmental and ecological systems. In this work, the hydrolytic stable Pb(II) CP {[Pb(asba)(obix)]•2H2O}n (1) [H2asba = 2-amino-4-sulfobenzoic acid, obix = 1, 2-(methylenebenzene)bisimidazole] was constructed and well characterized. 1 exhibits reversible de-/re-hydration behavior. The wide indirect band gap was obtained through the analysis of the solid-state diffuse reflectance UV–Vis spectrum of 1, which is consistent with the calculated value using the CASTEP program in Materials Studio. 1 keeps its crystallinity and structural integrity in various solvents. Interestingly, 1 shows solvent-dependent fluorescence emissions. A strong blue fluorescence emission occurs in water. 1 can sense the Fe3+ and chromate anions selectively and sensitively in the presence of the co-existent different metal cations and inorganic anions, respectively. Moreover, 1 also shows efficient sensing of Fe3+ in the simulative biological system. Furthermore, 1 demonstrates sensitive sensing of TNP. 1 displays excellent recyclability in sensing of these analytes. 1 can determine the related trace analytes in ppm level.

A dual-function probe BHMH was synthesized and characterized functioned with benzothiazole as signal unit for the simultaneous detection of Zn2+ and Al3+ DMF/H2O (1/1, v/v, 0.01 M HEPES, pH = 6.0). Probe BHMH achieved in the recognition of Zn2+ and Al3+ both through obvious fluorescence turn-on and absorbance ratiometric response. The limit of detection (LOD) according to the titration of fluorescence for Zn2+ and Al3+ were 1.27 × 10−7 M and 1.42 × 10−7 M, respectively. Furthermore, the significant color changes could be detected by naked eye whatever under ultraviolet-lamp or daylight. According to Job plot, the binding ratio of BHMH with Zn2+ and Al3+ were determined as 1:1 and 2:1, respectively. The binging detail was further confirmed by 1H NMR titration and ESI-MS analysis as well. Moreover, probe BHMH was successfully applied in the detection Zn2+ and Al3+ in real sample and test stripe.

Ring-opening polymerization (ROP) of cyclic peptide monomer of γ-propargyl-l-glutamate N-carboxyanhydride (PLG–NCA) was originally initiated by non-emissive, ring-close rhodamine 6G hydrazide (R-C). However, instantaneously after adding PLG–NCA to R-C, the spirolactam ring of R-C was opened by PLG–NCA, rendering emissive, ring-open R-O to initiate ROP of PLG–NCA. The emissive R-O moiety therefore produced fluorescent R–PLG with aggregation-induced emission (AIE) properties. Moreover, R–PLG was found to exhibit photochromic properties with good fatigue resistance and long lifetime when forming metal complexes with Sn(II) and Fe(III). In the dark, irradiated metal complexes slowly (~50 min) restored to the initial state. This research provides foundation for the development of new photochromic materials with long lifetime.

Two tri-armed piezochromic fluorescent molecules of tris(4-(4-phenylquinolin-2-yl)phenyl)amine (TPA-3Qu) and tris(4-(6-(9 H -carbazol-9-yl)-4-phenylquinolin-2-yl)phenyl)amine (TPA-3QuCz) were prepared and found to exhibit keen fluorescence responses toward compression. With the framework of a twisted, pyramidal triphenylamine (TPA) center connecting to three large quinolinecarbazole (QuCz) arms, the amorphous TPA-3QuCz exhibited a large bathochromic shift of 112 nm under gentle grinding forces, which is different from the small shift of 32 nm for TPA-3Qu under applying a relatively-large pressure of 10 MPa. Conformational transformations involving planarization of the arms were proposed to account for the observed fluorescence responses of TPA-3QuCz and TPA-3Qu towards pressure.

A new fluorescent probe capable of reliable detection of hydrazine under environmentally friendly conditions with high specificity and sensitivity was developed. 3,6-Diacetoxyfluoran (FDA), a readily commercially available compound, is explored for fluorescence “switch-on” detection of hydrazine in this work. FDA can undergo hydrazinolysis and transform into fluorescein in aqueous solution at neutral pH, resulting in distinct optical changes from colorless to green and “switch-on” fluorescence which allows for establishing a new method for sensitive detection of hydrazine. Under optimum conditions described in this work, the enhancement of fluorescence at 515 nm was linearly proportional to the concentrations of hydrazine ranging from 1.25 to 25.00 μM with a correlation coefficient of R2 = 0.9959 and a detection limit as low as 31 nM. The relative standard deviation of twelve replicate measurement samples was 5.4% for 12.5 μM hydrazine. The proposed method is convenient, low cost and free of complex equipment, making it possible to successfully determine hydrazine in four real samples containing distilled water, tap water, isoniazid and plasma. Furthermore, the hydrazine probe would be a promising candidate capable of naked-eye visualization of gaseous hydrazine by simple operations.

Restriction on molecular rotation of fluorophores reduces non-radiative decay channels and promotes strong fluorescence due to aggregation-enhanced emission (AEE) behavior. To evaluate the important role of restricted molecular rotation on AEE behavior, tetraphenylthiophene (TP) derivatives with two pyridine (Py) or two triphenylamine (TPA) terminals were synthesized and characterized to be AEE-active fluorophores. Because of the efficient hindered molecular rotation of the larger TPA terminals, TP-2TPA emitted with higher emission efficiency than TP-2Py with smaller Py terminals. In addition, Py and TPA terminals can serve as hydrogen-bond (H-bond) accepting groups to bind with H-bond donating hydroxyl groups in poly(vinyl phenol) (PVPh) and poly(vinyl alcohol) (PVA) to further reinforce rotational restriction on the TP-2Py and TP-2PTA fluorophores. TP-2Py and TP-2PTA were therefore blended with PVPh and PVA and the emissive properties of the resultant blends were characterized and compared with the unblended TP-2Py and TP-2PTA to emphasize the role of H-bond on restricted molecular rotation.

A new pyridine-terminated fluorophore of (E)-4-(2-(anthracen-9-yl)vinyl)pyridine (AnPy) with intramolecular charge transfer (ICT) and aggregation-induced emission (AIE) properties was synthesized and was blended with different amounts of polytyrosine (PTyr) through preferable hydrogen-bond (H-bond) interactions. In blends of a low AnPy content, the rigid PTyr peptide chains serve as templates to H-bond to AnPys, imposing rotational restriction and reinforcing the AIE-related emission intensity of AnPys, resulting in amorphous blends with the observed glass transitions dependent on the composition of the blends. In contrast, when large amounts of AnPys were added, excess AnPys will form new crystals, in between the amorphous regions, constituted of the near parallel dimers of AnPys. With the hampered molecular rotation, the parallel dimers of AnPys in the highly AnPy-loaded blends emit strongly with intensity much higher than those for the amorphous blends. In this study, conformations of the blends and the degree of restricted molecular rotation were assessed in order to correlate with the AIE-related fluorescence behaviour.

While most research has focused on the development of carbon dot (CD) based fluorescence sensors, much less attention has been paid to the phosphorescence phenomenon and its potential applications to date. Herein, room temperature phosphorescence (RTP) of water soluble CDs free of deoxidants and other inducers was observed for the first time in pure aqueous solution. RTP of CDs could be significantly quenched when chelating with iron ions as well as aggregation of CDs, presumably resulting from the formation of non-luminescent chelate. Due to a high affinity of iron ions to phosphate ions through well-known Fe–O–P bonds, the quenched RTP of functionalized CDs by Fe3+ could be basically recovered in the presence of phosphate-containing molecules. For a proof-of-concept demonstration, adenosine-5′-triphosphate (ATP), as a common phosphate-containing metabolite was quantitatively detected by a phosphorescence “off-to-on” approach. The enhancement of RTP at 440 nm was linearly proportional to the concentrations of ATP ranging from 20 to 200 μM with a detection limit as low as 14 μM. Moreover, the iron ion engineered CDs based RTP probe was used to estimate ATP levels in human blood plasma.

An organic azine derivative of CN4OH, containing both para- and ortho-hydroxyl (o- and p-OH) groups, is a fluorescent material with an emission efficiency dependent on the degree of crystallinity. With inherent hydroxyl groups, CN4OH can be homogeneously blended with different amounts of poly(4-vinyl pyridine) (PVP) through intermolecular hydrogen-bond (H-bond) interactions. With the incorporation of one and two molar equivalents of PVP, the solid CN4OH/PVP (4/1) and (2/1) blends emit strongly with intensity higher than pure CN4OH. Nevertheless, a further increase of the PVP content considerably reduced the crystallinity and the emission efficiency of the blend. Initially, PVP was preferably H-bonded to the p-OHs of CN4OH, resulting in the beneficial crystallization-enhanced emission (CEE); nevertheless, the PVP added in the later step started to bond to the o-OHs of CN4OH, reducing the crystallinity and the CEE-related fluorescence. With appropriate H-bond interactions, the CN4OH/PVP (2/1) blend emits with a high quantum yield (ΦF) of 88%, in contrast to the low ΦF of 15% for pure CN4OH.

Amphiphilic polymers with hydrophilic poly(N-isopropylacylamide) (PNIPAM) shell connecting hydrophobic tetraphenylthiophene (TP) core, which has the novel aggregation-induced emission (AIE) property, by ionic bonds were prepared to explore the AIE-operative emission responses toward critical micelle concentration (CMC) and lower critical solution temperature (LCST). To exercise the idea, ammonium-functionalized TP2NH(3)(+) and sulfonate-terminated PNIPAM were separately prepared and mixed in different molar ratios to yield three amphiphilic TP-PNIPAMn complexes for the evaluations of CMC and LCST by fluorescence responses. The nonemissive dilute aqueous solutions of TP-PNIPAMn became fluorescent when increasing concentrations above CMC. Heating micelles solution to temperatures above LCSTs causes further enhancement on the emission intensity. The fluorescence responses are explained by the extent of aggregation in the micelles and in the globules formed at room temperature and at high temperatures, respectively.

The study of the molecular weight (MW) fractions of dissolved organic matter (DOM) in aquatic environment is of interests because the size plays an important role in deciding the biogeochemical characteristics of DOM. Thus, using ultrafiltration ( UF) technique combined with three-dimensional fluorescence spectroscopy, DOM samples from four sampling sites in typical water-level fluctuation zones of Three Gorge Reservoir areas were selected to investigate the differences of properties and sources of different DOM MW fractions. The results showed that in these areas, the distribution of MW fractions was highly dispersive, but the approximately equal contributions from colloidal (Mr 1 x 10³-0.22 µm) and true dissolved fraction (Mr1 x 10³) to the total DOC concentration were found. Four fluorescence signals (humic-like A and C; protein-like B and T) were observed in all MW fractions including bulk DOM, which showed the same distribution trend: true dissolvedlow MW (Mr 1 x 10³-10 x 10³)medium MW (Mr 10 x 10³-30 x 10³)high MW (Mr 30 x 10³-0.22 µm). Additionally, with decreasing MW fraction, fluorescence index (FI) and freshness index (BIX) increased suggesting enhanced signals of autochthonous inputs, whereas humification index ( HIX) decreased indicating lowe humification degree. It strongly suggested that terrestrial input mainly affected the composition and property of higher MW fractions of DOM, as compared to lower MW and true dissolved fractions that were controlled by autochthonous sources such as microbial and alga activities, instead of allochthonous sources. Meanwhile, the riparian different land-use types also affected obviously on the characteristics of DOM. Therefore, higher diversity of land-use types, and also higher complexity of ecosystem and landscapes, induced higher heterogeneity of fluorescence components in different MW fraction of DOM.

While the super fluorescence quenching capacity of graphene and graphene oxide (GO) has been extensively employed to develop fluorescent sensors, their own unique fluorescence and its potential for chemo-/biosensing have seldom been explored. Here we report a GO-based photoinduced charge transfer (PCT) label-free near-infrared (near-IR) fluorescent biosensor for dopamine (DA). The multiple noncovalent interactions between GO and DA and the ultrafast decay at the picosecond range of the near-IR fluorescence of GO resulted in effective self-assembly of DA molecules on the surface of GO, and significant fluorescence quenching, allowing development of a PCT-based biosensor with direct readout of the near-IR fluorescence of GO for selective and sensitive detection of DA. The developed method gave a detection limit of 94 nM and a relative standard deviation of 2.0% for 11 replicate detections of 2.0 μM DA and was successfully applied to the determination of DA in biological fluids with quantitative recovery (98-115%).

In this study, fluorescent alternative copolymer poly(fluorene-alt-1,6-naphthol) (PFN) with inherent hydroxyl (OH) groups was blended with poly(vinyl pyrrolidone) (PVR) through facile hydrogen-bond (H-bond) interactions. The emission intensities of the resultant PFN/PVR mixtures of different compositions were shown to increase with increasing PVR content in both the chloroform solution and in the solid film states. The H-bond interactions between PFN and PVR resulted in the restricted molecular rotations of the fluorophores, which lead to the blockage of nonradiative energy decay channels and the accompanied emission enhancement. With the efficient H-bond interactions, the PFN/PVR blend with the low content (2.33 wt %) of fluorescent PFN component actually has a high quantum efficiency of 0.93, comparatively higher than other blends containing higher fluorescent PFN. The role of the H-bonding on the restricted molecular rotations of the PFN/PVR blends was therefore evaluated by the infrared, the 1H NMR sp...

A hydrophobic tetraphenylthiophene (TP) center with novel aggregation-induced emission (AIE) property was chemically linked to two poly(N-isoprppylacrylamide) (PNIPAM) chains to obtain thermoresponsive polymers to study the relationships between the lower critical solution transitions (LCSTs) and the AIE-operative fluorenscence (FL) emission. Three ethynyl-terminated PNIPAMs with different molecular weights were synthesized via controlled atom transfer radical polymerization (ATRP) using ethynyl-functionalized initiator. The PNIPAMs were then coupled with diazide-funtionalized TP (TPN3) via click reaction to obtain the desired TP-embedded polymers of Px (x = 1, 2, and 3). All three polymers show AIE-property from their solution fluorescence behavior in THF/hexane mixtures. In the aqueous solution, the TP-center served as a fluorogenic probe that reveals the LCSTs of polymers and its relation to the degree of TP labeling in terms of polymer concentration. The thermoresponsiveness of Px was demonstrated by ...

In this study, fluorescent organic compound FN and polymer PFN with alternative fluorene and naphthol units were prepared to assess the influence of the hydrogen bonds (H-bonds) on the emission behavior. Both FN and PFN exhibit the enhanced aggregation emission behavior with enhanced emissions on solution mixtures of higher degree of aggregation. For solid FN and PFN films, the fractions of the H-bonded hydroxyl groups decrease upon being heated to high temperature, which results in aggregate dissociation and reductions in the aggregation emissions. Meanwhile, procedures leading to the increase of the H-bonds (such as shearing or enhanced aggregation by addition of nonsolvent in the solution preparative step) resulted in solid films with higher emission intensity. Variations on the H-bonds can be detected by infrared spectroscopy and are in line with the emission behavior.

Two fluorescent anion receptors (1 and 2) based on amide macrocycle were synthesized and corresponding fluorescence quenching induced by anion complexation was observed in different degree. Receptors form 1:1 complexes with anions by hydrogen bonding interactions. Receptor 1 bound anions in the order of F->Cl- > H2PO4−- CH3COO− > >Br−, I− and receptor 2 showed high selectivity to F− over other anions.

Two new neutral receptors (1 and 2) containing (thio) urea and amide groups were synthesized by simple steps in good yields. The binding properties for anions of 1 and 2 were characterized by UV-vis and fluorescence spectra. Receptor 1 had an excellent selectivity for AcO− in comparison with other anions. The association constants of 1 · AcO− and 2 · p-NO2PhOPO23− were higher than those of other anions (Cl−, Br−, I−, H2PO−4 and p-NO2PhO−). In particular, an obvious color change was observed from light yellow to golden yellow upon addition of AcO− to the solution of 1 in DMSO. The results of non-linear curve fitting by UV-vis and fluorescence spectral data indicate that a 1:1 stoichiometry complex is formed between compound 1 or 2 and anions through a hydrogen bonding interaction.

Salicylaldehyde rhodamine B hydrazone (SRBH) was developed as a new spectrofluorimetric probe for the selective and sensitive detection of CrO(4)(2-) in acidic conditions. The proposed method was based on the special oxidation reaction between non-fluorescent SRBH by potassium dichromate to produce a highly fluorescent rhodamine B, as a product. Under the optimum conditions described, the fluorescence enhancement at 591 nm was good linearly related to the concentration of CrO(4)(2-) from 1.0 x 10(-8) to 3.0 x 10(-7)M (0.42-12.6 ng mL(-1)) with a correlation coefficient of R(2)=0.9989 (n=10) and a detection limit of 1.5 x 10(-9)M (0.063 ng mL(-1)). The relative standard deviation (R.S.D.) was 2.0% (n=6). The proposed method was also successfully applied to the determination of chromium (VI) in drinking water, river water and synthetic samples.

Water-soluble fluorescent CdTe nanorods (NRs) capped with L-cysteine (Cys) and thioglycolic acid (TGA) were prepared for optical determination of silver ions. These NRs are dispersible, uniform and strongly fluorescent, with an emission wavelength maximum of 585 nm. The fluorescence of such NRs is quenched by silver ions, and this is accompanied by a gradual red shift of the peak from 585 nm to 605 nm. The limit of determination for silver ions is 4.5 nM. The effect of alkali and alkali earth metal ions and of common anions is negligible even at high concentrations. Steady-state fluorescence and UV-vis spectroscopy reveals that competitive binding of Ag ions to Te atoms and to Cys/TGA moieties are responsible for the change in the optical properties observed.

Monodisperse and “naked” gold nanoparticles (GNPs) were modified with thioglycolic acid (TGA). The fluorescence of rhodamine B (RB) is quenched completely by the gold NPs surface with negative charge mainly as a result of fluorescence resonance energy transition (FRET) and collision. The quenching mechanism can be described by a Langmuir isotherm, which was systematically investigated by steady-state fluorescence spectrometry and absorption spectrometry. Hg(II) ion disrupts the GNPs–RB pair, producing a large “switch-on” fluorescence. A low background, highly sensitive and reproducible fluorescence assay for Hg(II) is presented. Under the optimum conditions, the restoration fluorescence intensity is proportional to the concentration of Hg(II). The calibration graphs are linear over the range of 1.0 × 10−9 to 3.1 × 10−8 mol L−1 with a detection limit of 4.0 × 10−10 mol L−1. The relative standard deviation was 1.2% for a 5.0 × 10−9 mol L−1 Hg(II) solution (N = 6). This method was applied to the analysis of Hg(II) in environmental water samples, and the results were consistent with those of atomic absorption spectroscopy (AAS).

Strong luminescence CdS quantum dots (QDs) have been prepared and modified with l-cysteine by a facile seeds-assistant technique in water. They are water-soluble and highly stable in aqueous solution. CdS QDs evaluated as a luminescence probe for heavy and transition metal (HTM) ions in aqueous solution was systematically studied. Five HTM ions such as silver(I) ion, copper(II) ion, mercury(II) ion, cobalt(II) ion, and nickel(II) ion significantly influence the photophysics of the emission from the functionalized CdS QDs. Experiment results showed that the fluorescence emission from CdS QDs was enhanced significantly by silver ion without any spectral shift, while several other bivalent HTM ions, such as Hg(2+), Cu(2+), Co(2+), and Ni(2+), exhibited effective optical quenching effect on QDs. Moreover, an obvious red-shift of emission band was observed in the quenching of CdS QDs for Hg(2+) and Cu(2+) ions. Under the optimal conditions, the response was linearly proportional to the concentration of Ag(+) ion ranging from 1.25 x 10(-7) to 5.0 x 10(-6)molL(-1) with a detection limit of 2.0 x 10(-8)molL(-1). The concentration dependence of the quenching effect on functionalized QDs for the other four HTM ions could be well described by typical Stern-Volmer equation, with the linear response of CdS QDs emission proportional to the concentration ranging from 1.50 x 10(-8) to 7.50 x 10(-7)molL(-1) for Hg(2+) ion, 3.0 x 10(-7) to 1.0 x 10(-5)molL(-1) for Ni(2+) ion, 4.59 x 10(-8) to 2.295 x 10(-6)molL(-1) for Cu(2+) ion, and 1.20 x 10(-7) to 6.0 x 10(-6)molL(-1) Co(2+) ion, respectively. Based on the distinct optical properties of CdS QDs system with the five HTM ions, and the relatively wide linear range and rapid response to HTM ions, CdS QDs can be developed as a potential identified luminescence probe for familiar HTM ions detection in aqueous solution.

Highly luminescent uncoated water-soluble and mono-disperse CdSe nanoparticles (NPs) have been prepared facilely. Uncoated CdSe core NPs possessing a good size distribution was accompanied with long wavelength of fluorescence emission. It is interesting to note that these functionalized NPs are soluble in water medium stably for more than 1 month, and no significant changes were found in the optical characteristics in comparison with fresh CdSe NPs prepared. The functionalized CdSe NPs exhibited strong specific affinity for mercury(II) through their surface functional groups. Based on the significant quenching of fluorescence emission of functionalized CdSe NPs with a long-wavelength 630nm, a simple, rapid and specific detection for Hg(II) was proposed. Under optimum conditions, the response of linearly proportional to the concentration of Hg(II) is between 0mol/L and 1.25x10(-6)mol/L, and the limit of detection is 4.50x10(-9)mol/L. The relative standard deviation (R.S.D.) of six replicate measurements is 2.0% for 2.0x10(-7)mol/L of Hg(II). In terms of fluorescence quenching at 630nm of CdSe NPs, no obvious wavelength shift or no new emission band in presence of Hg(II) at pH 7.50 of phosphate buffer solution were found; furthermore, a significant reduction in absorbance at 230nm of CdSe NPs was first observed in our work. We could speculate that Hg(II) as an effective quencher (even at low concentration) for functionalized CdSe NPs emission suggests that it is capable of directly intercepting one of the charge carriers, thus disrupting the recombination process.

As an important geo-factor to decide the environmental fate of pollutants in watershed, soil dissolved organic matter (DOM) sampled from a typical agricultural watershed in the Three Gorges Reservoir area was investigated using ultraviolet-visible (UV-Vis) and fluorescence spectroscopies, to analyze and discuss the effect of different land uses including forest, cropland, vegetable field and residence, on soil DOM geochemical characteristics. The results showed that significant differences in DOM samples amongst different land uses were observed, and DOM from forest had the highest aromaticity and humification degree, followed by DOM from cropland. Although DOM from vegetable field and residence showed the highest dissolved organic carbon (DOC) concentration (average values 0.81 g x kg(-1) and 0.89 g x kg(-1), respectively), but the aromaticity was lower indicating lower humification, which further suggested that the non-chromophoric component in these DOM samples contributed significantly to total DOM compositions. Additionally, in all DOM samples that were independent of land uses, fluorescence index (FI) values were between 1.4 (terrigenous) and 1.9 (authigenic) , evidently indicating both the allochthonous and autochthonous sources contributed to DOM characteristics. Meanwhile, r(T/C) values in most of samples were higher than 2.0, suggesting that soil DOM in this agricultural watershed was heavily affected by anthropogenic activities such as agricultural cultivation, especially, vegetable field was a good example. Additionally, sensitivities of different special spectral parameters for reflecting the differences of DOM characteristics amongst different land uses were not identical. For example, neither spectral slope ratio (S(R)) nor humification index (HIX) could clearly unveil the various geochemical characteristics of soil DOM from different sources. Thus, simple and single special spectral parameter cannot comprehensively provide the detailed information of DOM, and combined application of UV-Vis and fluorescence spectroscopies is highly recommended.

Three-dimensional fluorescence spectroscopy combined with ultraviolet-visible (UV-Vis) absorption spectra was used to investigate the change characteristics of dissolved organic matter (DOM) in confluences water of Qujiang River-Jialing River and Fujiang River-Jialing River, respectively. The results suggested that DOM showed a significant terrestrial input signal in all the sampling sites, FI1.4, HIX0.8, possibly representing remarkable signals of humus resulted from humic-like component. Moreover, the mixing zone of this study showed a non-conservative mixed behavior, which had a limited contribution, and was not the dominant factor to interpret the change characteristics of DOM in confluences zones. Different land-use types along all the rivers had an obvious impact on DOM inputs. Results of cluster analysis showed that a higher degree of aromaticity and humification components was observed as the predominant contributor to DOM when the land-use type was forest and farmland ecosystem, for example the confluences of Qujiang River-Jialing River. On the other hand, high concentrations of DOM with relative simple structures were found in the water when the urban land-use type was predominant, for example the confluences of Fujiang River-Jialing River. Meanwhile, a new fluorescent signal of protein-like components (peak T) appeared, which manifested a significant effect on the water quality resulted from anthropogenic activities.

This study aimed at evaluating the variability of the optical properties including UV-Vis and fluorescence characteristics of dissolved organic matter (DOM) from rainwater in summer and winter seasons. UV-Vis and fluorescence spectroscopy, together with Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and fire events map, were conducted to characterize DOM and investigate its sources and contributions. The results showed that as compared with aquatic and soil DOM, rainwater DOM showed similar spectral characteristics, suggesting DOM in precipitation was also an important contributor to DOM pool in terrestrial and aquatic systems. The concentrations of DOC in rainwater were 0.88-12.80 mg x L(-1), and the CDOM concentrations were 3.17-21.11 mg x L(-1). Differences of DOM samples between summer and winter were significant (P0.05). In comparison to summer, DOM samples in winter had lower molecular weight and aromaticity, and also lower humification. Input of DOM in winter was predominantly derived from local and short-distance distances, while non-special scattering sources were identified as the main contributors in summer. Although absorption and fluorescence spectroscopy could be used to identify DOM composition and sources, there were obvious differences in spectra and sources analysis between rainwater DOM and the others from other sources. Thus, the classic differentiation method by "allochthonous (terrigenous) and autochthonous (authigenic)" is possibly too simple and arbitrary for characterization of DOM in rainwater.

Pyrene-tetramethylpiperidinyl (Pyr-Tempo) as a spin label fluorescent probe for iron(II) was synthesized. It exhibited weak fluorescence (λexc/λem = 346/399 nm) in aqueous solution due to an intramolecular quenching pathway. A method for determination of iron(II) was proposed based on the fluorescence enhancement of the probe in the presence of iron(II) in acidic medium. Under optimum conditions, the fluorescence enhancement of Pyr-Tempo is linearly proportional to the iron(II) concentration range of 6.0 × 10−8 to 9.6 × 10−6 mol L−1 with a detection limit of 8.0 × 10−9 mol L−1. The relative standard deviation (RSD) of six replicate measurements is 1.95% for 3.0 × 10−7 mol L−1 iron(II). The developed spin label fluorescence probe is found to be rapidly and sensitively responsive to iron(II) with high selectivity compared to existing fluorescence methods. The proposed method was successfully applied to iron(II) detection in five real samples with satisfactory results obtained by manual UV/Vis spectrophotometry (standard method) with 1,10-phenanthroline.